Catalytic and Stimulative Effects of Molecular Sieve 13X on Promoted Humification during Composting

Enhancing humification during composting is vital for boosting fertilizer value and achieving resource recycling. To address the limited availability of effective humification-promoting additives, we investigated the application of molecular sieve 13X and found that trace addition of 13X during composting resulted in a significant elevation of humification. With an economical dosage of 13X (0.05 wt %), the content of humic acid (HA) and HA/fulvic acid ratio (HA/FA) were increased by 18.1 and 59.6%, respectively. Subsequently, we optimized the timing of 13X addition and found that implementing halfway addition at the thermophilic or cooling phase of composting yielded superior humification results over early addition at the initial heating phase. We explored and interpreted the mechanisms underlying the enhanced humification from both chemical and biological perspectives. Chemically, 13X catalyzed the polyphenol-Maillard reaction, thereby enhancing the polymerization of precursor substances into HA, wherein the surface acidic sites of 13X played a crucial role. Biologically, 13X stimulated the compost microbial community and enriched the bacteria associated with humification, thereby promoting the formation of HA. This work demonstrates that molecular sieve materials could serve as a promising composting stimulant via promoting humification to achieve value-added conversion of organic solid wastes to resources.